/*
 * Copyright (C) 2008 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import java.util.Collection;
import java.util.Comparator;
import java.util.NoSuchElementException;
import java.util.Set;

import javax.annotation.Nullable;

import com.google.common.annotations.GwtCompatible;

/**
 * An empty immutable sorted set.
 * 
 * @author Jared Levy
 */
@GwtCompatible(serializable = true)
@SuppressWarnings("serial")
// uses writeReplace(), not default serialization
class EmptyImmutableSortedSet<E> extends ImmutableSortedSet<E> {
    EmptyImmutableSortedSet(Comparator<? super E> comparator) {
        super(comparator);
    }

    public int size() {
        return 0;
    }

    @Override
    public boolean isEmpty() {
        return true;
    }

    @Override
    public boolean contains(Object target) {
        return false;
    }

    @Override
    public UnmodifiableIterator<E> iterator() {
        return Iterators.emptyIterator();
    }

    private static final Object[] EMPTY_ARRAY = new Object[0];

    @Override
    public Object[] toArray() {
        return EMPTY_ARRAY;
    }

    @Override
    public <T> T[] toArray(T[] a) {
        if (a.length > 0) {
            a[0] = null;
        }
        return a;
    }

    @Override
    public boolean containsAll(Collection<?> targets) {
        return targets.isEmpty();
    }

    @Override
    public boolean equals(@Nullable Object object) {
        if (object instanceof Set) {
            Set<?> that = (Set<?>) object;
            return that.isEmpty();
        }
        return false;
    }

    @Override
    public int hashCode() {
        return 0;
    }

    @Override
    public String toString() {
        return "[]";
    }

    public E first() {
        throw new NoSuchElementException();
    }

    public E last() {
        throw new NoSuchElementException();
    }

    @Override
    ImmutableSortedSet<E> headSetImpl(E toElement) {
        return this;
    }

    @Override
    ImmutableSortedSet<E> subSetImpl(E fromElement, E toElement) {
        return this;
    }

    @Override
    ImmutableSortedSet<E> tailSetImpl(E fromElement) {
        return this;
    }

    @Override
    boolean hasPartialArray() {
        return false;
    }

    @Override
    int indexOf(Object target) {
        return -1;
    }
}
